In the forestry, lumber and pulp and paper industry, it is common at present to fell trees one tree at a time. There are varying methods of collecting the trees into bunches and of loading the trees for subsequent transport or processing, and generally the yield is from two to six trees per minute.
There have been some attempts to apply to tree felling the idea of a continuously travelling and collecting machine, similar to a combine or forage harvester used in agriculture. A first thought along this line might be to provide a machine with a full width tree cutting sickle bar, and a gathering and carrying mechanism. However, this has apparently not been attempted due to the variability of terrain and the difficulty of manoeuvring such a wide-width machine. Instead, there have been attempts to exploit the continuous felling pinciple by bringing the swath width down to a manageable size. By decreasing the swath width, one must increase the speed of the machine in order to keep the yield acceptably high. Reference may be had here to Canadian Pat. No. 1,029,283, granted on Apr. 11, 1978, Hyde and Tyndall, and U.S. Pat. No. 3,659,635, granted on May 2, 1972, Mellgren. The approach in the latter patent is to mount a circular cutting saw blade in a horizontal plane adjacent the machine, and to run the machine forward as the circular saw blade cuts a swath adjacent the path followed by the machine. The circular saw blade is mounted to pass closely over the surface of the ground, thereby cutting the trees off as close to the roots as possible.
This narrow swath/high speed approach to continuous tree felling has been limited to exceptionally good terrain, and for most applications it is therefore desirable to return to the concept of a wide swath, such as can be attained by the use of a boom. Unlike conventional shear or saw heads, however, such a boom should have means which permit continuous tree felling, and multiple tree accumulation if the trees are of small enough diameter, while the harvesting machine travels at a low speed through the forest. This would result in low miles per hour, low cost per mile, low miles per acre, and low cost per acre.